U.S. patent number 10,935,912 [Application Number 16/817,509] was granted by the patent office on 2021-03-02 for heating device having first and second heat transfer units for an image forming unit.
This patent grant is currently assigned to TOSHIBA TEC KABUSHIKI KAISHA. The grantee listed for this patent is TOSHIBA TEC KABUSHIKI KAISHA. Invention is credited to Shuji Yokoyama.
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United States Patent |
10,935,912 |
Yokoyama |
March 2, 2021 |
Heating device having first and second heat transfer units for an
image forming unit
Abstract
According to one embodiment, a heating device includes a
cylindrical body, a heater unit, a support member, a first heat
transfer unit, and a second heat transfer unit. The cylindrical
body has a film shape. The heater unit is disposed inside the
cylindrical body. In the heater unit, the axial direction of the
cylindrical body is taken as a longitudinal direction. The support
member supports the heater unit. The first heat transfer unit is
disposed between the inner surface of the cylindrical body and the
heater unit. The first heat transfer unit abuts on a first surface
of the heater unit. The second heat transfer unit is disposed
between the heater unit and the support member. The second heat
transfer unit abuts on a second surface of the heater unit opposite
to the first surface.
Inventors: |
Yokoyama; Shuji (Sunto
Shizuoka, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
TOSHIBA TEC KABUSHIKI KAISHA |
Tokyo |
N/A |
JP |
|
|
Assignee: |
TOSHIBA TEC KABUSHIKI KAISHA
(Tokyo, JP)
|
Family
ID: |
1000004718387 |
Appl.
No.: |
16/817,509 |
Filed: |
March 12, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03G
15/2053 (20130101); G03G 15/2064 (20130101); G03G
2215/2025 (20130101); G03G 2215/2035 (20130101) |
Current International
Class: |
G03G
15/20 (20060101) |
Field of
Search: |
;399/329 ;219/216 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
|
2013068724 |
|
Apr 2013 |
|
JP |
|
2015-079202 |
|
Apr 2015 |
|
JP |
|
2015145950 |
|
Aug 2015 |
|
JP |
|
2016095397 |
|
May 2016 |
|
JP |
|
2016161849 |
|
Sep 2016 |
|
JP |
|
2019091028 |
|
Jun 2019 |
|
JP |
|
Primary Examiner: Beatty; Robert B
Attorney, Agent or Firm: Foley & Lardner LLP
Claims
What is claimed is:
1. A heating device for an image forming unit, the heating device
comprising: a roller centered on a first center axis; a heater
unit; a cylindrical film at least partially disposed around the
heater unit, the cylindrical film centered on a second center axis,
the second center axis parallel to the first center axis; a support
member configured to support the heater unit above the cylindrical
film and such that the heater unit is located between the support
member and the cylindrical film; a first heat transfer unit
disposed between the cylindrical film and the heater unit and in
confronting relation with a first surface of the heater unit; and a
second heat transfer unit disposed between the heater unit and the
support member and in confronting relation with a second surface of
the heater unit, the second surface opposite the first surface;
wherein the heater unit is centered on a third center axis, the
third center axis being parallel to a line that intersects the
first center axis and the second center axis, and the third center
axis being offset from the line such that a sheet fed between the
roller and the cylindrical film intersects the line before
intersecting the third center axis.
2. The heating device of claim 1, wherein: the first heat transfer
unit has a first thermal conductivity; the second heat transfer
unit has a second thermal conductivity; and the first thermal
conductivity is greater than the second thermal conductivity.
3. The heating device of claim 1, wherein: the first heat transfer
unit has a first thermal conductivity; the second heat transfer
unit has a second thermal conductivity; the heater unit comprises a
substrate in confronting relation with the second heat transfer
unit, the substrate having a third thermal conductivity; the first
thermal conductivity is greater than the third thermal
conductivity; and the second thermal conductivity is greater than
the third thermal conductivity.
4. The heating device of claim 1, wherein the heater unit
comprises: a substrate in confronting relation with the second heat
transfer unit; and a heating element disposed on the substrate, the
heating element in confronting relation with the first heat
transfer unit.
5. The heating device of claim 1, further comprising a lubricating
layer disposed between the cylindrical film and the first heat
transfer unit.
6. The heating device of claim 5, wherein a thickness of the
lubricating layer is greater than or equal to 1 .mu.m and less than
or equal to 100 .mu.m.
7. The heating device of claim 1, wherein: the second heat transfer
unit has a first contact area with the support member; the first
heat transfer unit has a second contact area with the heater unit;
and the first contact area is smaller than the second contact
area.
8. The heating device of claim 1, wherein: the first heat transfer
unit is a plate-shaped first heat absorbing member and is centered
on a fourth center axis; the fourth center axis is orthogonal to
the second center axis; and the second heat transfer unit is a
plate-shaped second heat absorbing member and is structurally
separable from the first heat transfer unit.
9. The heating device of claim 1, wherein: the first heat transfer
unit is integrally formed with the second heat transfer unit in a
heat absorbing member; and the heat absorbing member has a U-shape
that partially extends around the heater unit.
10. An image processing apparatus comprising the heating device of
claim 1.
11. A heating device for an image forming unit, the heating device
comprising: a roller centered on a first center axis; a film
centered on a second center axis, the second center axis parallel
to the first center axis; a support separated from the roller by
the film; a heater unit coupled to the support and centered on a
third center axis, the third center axis being parallel to a line
that intersects the first center axis and the second center axis,
and the third center axis being offset from the line such that a
sheet fed between the roller and the film intersects the line
before intersecting the third center axis; a first transfer member
coupled to at least one of: the support or the heater unit, the
first transfer member separating the heater unit from the film; and
a second transfer member coupled to at least one of: the support or
the heater unit, the second transfer member separating the heater
unit from the support.
12. The heating device of claim 11, wherein: the second transfer
member is separated from the first transfer member by the heater
unit; the first transfer member has a first thermal conductivity;
the second transfer member has a second thermal conductivity; and
the second thermal conductivity is less than the first thermal
conductivity.
13. The heating device of claim 11, further comprising a thermostat
coupled to at least one of: the support or the second transfer
member, the thermostat configured to determine a temperature of the
second transfer member; wherein the roller comprises: a cored bar;
and an elastic layer extending around the cored bar, the elastic
layer separating the cored bar from the film and configured to be
compressed against the cored bar.
14. The heating device of claim 11, wherein the heater unit
comprises: a substrate in confronting relation with the second
transfer unit; an insulating layer coupled to the substrate and
separated from the second transfer unit by the substrate; a heating
element coupled to the insulating layer and separated from the
substrate by the insulating layer; and a protective layer coupled
to the heating element and the insulating layer, the protective
layer separated from the substrate by the insulating layer.
15. A heating device for an image forming unit, the heating device
comprising: a heater unit comprising: a substrate; an insulating
layer coupled to the substrate; a heating element coupled to the
insulating layer and separated from the substrate by the insulating
layer; and a protective layer coupled to the heating element and
the insulating layer, the protective layer separated from the
substrate by the insulating layer; a film extending at least
partially around the heater unit; a first transfer member coupled
to the heater unit and separating the heater unit from the film;
and a second transfer member coupled to the substrate and separated
from the insulating layer by the substrate, the second transfer
member being integrally formed with the first transfer member such
that a cavity is defined between the first transfer member and the
second transfer member; wherein the heater unit is at least
partially disposed within the cavity.
16. The heating device of claim 15, further comprising a thermostat
coupled to the second transfer member, the thermostat configured to
determine a temperature of the second transfer member.
17. The heating device of claim 15, wherein: the film is centered
on a first center axis; the heater unit is centered on a second
center axis; and the second center axis is orthogonal to the first
center axis.
Description
FIELD
Embodiments described herein relate generally to a heating device
and an image processing apparatus.
BACKGROUND
An image forming apparatus can be used to form an image on a sheet.
The image forming apparatus can be an image processing apparatus.
The image forming apparatus includes a heating device for fixing
toner (recording agent) to a sheet. The heating device includes a
cylindrical body and a heater unit. The cylindrical body has a film
shape. The heater unit is disposed inside the cylindrical body. In
the heater unit, the axial direction of the cylindrical body is
taken as a longitudinal direction. When a sheet passing through the
heating device is heated, a temperature distribution is generated
in the heater unit according to the size of the sheet. The heating
device is required to distribute the temperature distribution of
the heater unit.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic configuration diagram of an image processing
apparatus according to an embodiment;
FIG. 2 is a hardware configuration diagram of the image processing
apparatus;
FIG. 3 is a front cross-sectional view of a heating device;
FIG. 4 is a front cross-sectional view of a heater unit;
FIG. 5 is a bottom view of the heater unit;
FIG. 6 is a plan view of a heater thermometer and a thermostat;
FIG. 7 is an electric circuit diagram of the heating device;
FIG. 8 is a front cross-sectional view of a heating device
according to a first modification example of the embodiment;
and
FIG. 9 is a front cross-sectional view of a heating device
according to a second modification example of the embodiment.
DETAILED DESCRIPTION
In general, according to one embodiment, a heating device includes
a cylindrical body, a heater unit, a support member, a first heat
transfer unit, and a second heat transfer unit. The cylindrical
body has a film shape. The heater unit is disposed inside the
cylindrical body. In the heater unit, the axial direction of the
cylindrical body is taken as a longitudinal direction. The support
member supports the heater unit. The first heat transfer unit is
disposed between the inner surface of the cylindrical body and the
heater unit. The first heat transfer unit abuts on a first surface
of the heater unit. The second heat transfer unit is disposed
between the heater unit and the support member. The second heat
transfer unit abuts on a second surface of the heater unit opposite
to the first surface.
Hereinafter, a heating device and an image processing apparatus
according to an embodiment will be described with reference to the
drawings.
FIG. 1 is a schematic configuration diagram of the image processing
apparatus according to the embodiment.
The image processing apparatus according to the embodiment is an
image forming apparatus 1. The image forming apparatus 1 performs a
process of forming an image on a sheet (paper) S. In various
embodiments, the sheet S is a sheet of paper, such as printer
paper.
The image forming apparatus 1 includes a housing 10, a scanner unit
2, an image forming unit 3, a sheet supply unit 4, a conveyance
unit 5, a sheet discharge tray 7, a reversing unit 9, a control
panel 8, and a control unit 6.
The housing 10 forms the outer shape of the image forming apparatus
1. For example, the housing 10 may enclose (e.g., encapsulate,
surround, cover, etc.) various other components of the image
forming apparatus 1 such as the scanner unit 2, the image forming
unit 3, the sheet supply unit 4, the conveyance unit 5, the sheet
discharge tray 7, the reversing unit 9, the control panel 8, or the
control unit 6.
The scanner unit 2 reads (obtains) image information of an object
to be copied as light contrast, and generates an image signal. The
scanner unit 2 outputs the generated image signal to the image
forming unit 3.
The image forming unit 3 forms an output image (hereinafter
referred to as a toner image) by a recording agent such as toner
based on the image signal received from the scanner unit 2 or an
image signal received from the outside, such as from an external
device or via a network. The image forming unit 3 transfers the
toner image onto the front surface of the sheet S. The image
forming unit 3 heats and pressurizes the toner image on the front
surface of the sheet S to fix the toner image on the sheet S.
Details of the image forming unit 3 will be described later.
The sheet supply unit 4 supplies sheets S to the conveyance unit 5
one by one in accordance with the timing at which the image forming
unit 3 forms a toner image. The sheet supply unit 4 includes a
sheet storage unit 20 and a pickup roller 21.
The sheet storage unit 20 stores sheets S having a predetermined
size (target size) and type (target type).
The pickup roller 21 picks up the sheets S from the sheet storage
unit 20 one by one. The pickup roller 21 supplies the picked-up
sheet S to the conveyance unit 5.
The conveyance unit 5 conveys the sheet S supplied from the sheet
supply unit 4 to the image forming unit 3. The conveyance unit 5
includes a conveyance roller 23 and a registration roller 24.
The conveyance roller 23 conveys the sheet S supplied from the
pickup roller 21 to the registration roller 24. The conveyance
roller 23 abuts the front end of the sheet S in the conveyance
direction against a nip N of the registration rollers 24.
The registration roller 24 adjusts the position of the front end of
the sheet S in the conveyance direction by bending the sheet S at
the nip N. The registration roller 24 conveys the sheet S in
accordance with the timing at which the image forming unit 3
transfers the toner image to the sheet S. The image forming unit 3
will be described.
The image forming unit 3 includes a plurality of image forming
sections 25, a laser scanning unit 26, an intermediate transfer
belt 27, a transfer unit 28, and a fixing device 30 (heating
device).
The image forming section 25 includes a photosensitive drum 25d.
The image forming section 25 forms a toner image corresponding to
the image signal from the scanner unit 2 or the outside on the
photosensitive drum 25d. A plurality of image forming sections 25Y,
25M, 25C, and 25K form toner images with yellow, magenta, cyan, and
black toners, respectively.
A charger, a developing device, and the like are disposed around
the photosensitive drum 25d. The charger charges the front surface
of the photosensitive drum 25d. The developing device contains a
developer including yellow, magenta, cyan, and black toners. The
developing device develops an electrostatic latent image on the
photosensitive drum. 25d. As a result, a toner image is formed with
a toner of each color on the photosensitive drum 25d.
The laser scanning unit 26 scans the charged photosensitive drum
25d with a laser beam L to expose (activate) the photosensitive
drum 25d. The laser scanning unit 26 exposes the photosensitive
drums 25d of the image forming sections 25Y, 25M, 25C, and 25K of
the respective colors with different laser beams LY, LM, LC, and
LK. As a result, the laser scanning unit 26 forms an electrostatic
latent image on the photosensitive drum 25d. The toner image on the
front surface of the photosensitive drum 25d is primarily
transferred onto the intermediate transfer belt 27.
The transfer unit 28 transfers the toner image primarily
transferred onto the intermediate transfer belt 27 onto the front
surface of the sheet S at a secondary transfer position.
The fixing device 30 heats and pressurizes the toner image
transferred onto the sheet S to fix the toner image to the sheet S.
Details of the fixing device 30 will be described later. The
reversing unit 9 reverses (flips) the sheet S in order to form an
image on the back surface of the sheet S. The reversing unit 9
reverses the sheet S discharged from the fixing device 30 with a
switch mechanism (switch back). The reversing unit 9 conveys the
reversed sheet S toward the registration roller 24.
The sheet discharge tray 7 receives the sheet S on which an image
is formed and provides the sheet S for discharge from the image
forming apparatus 1.
The control panel 8 is a part of an input unit for inputting
information for an operator to operate the image forming apparatus
1. The control panel 8 includes a touch panel and various hard
keys.
The control unit 6 controls each unit of the image forming
apparatus 1. Details of the control unit 6 will be described
later.
FIG. 2 is a hardware configuration diagram of the image processing
apparatus according to the embodiment. The image forming apparatus
1 includes a central processing unit (CPU) 91, a memory 92, an
auxiliary storage device 93, and the like, which are connected by a
bus. The image forming apparatus 1 executes a program. The image
forming apparatus 1 functions as an apparatus including the scanner
unit 2, the image forming unit 3, the sheet supply unit 4, the
conveyance unit 5, the reversing unit 9, the control panel 8, and a
communication unit 90 by executing a program.
The CPU 91 functions as the control unit 6 by executing a program
stored in the memory 92 and/or the auxiliary storage device 93. The
control unit 6 controls the operation of each functional component
of the image forming apparatus 1, such as the scanner unit 2, the
image forming unit 3, the sheet supply unit 4, the conveyance unit
5, the reversing unit 9, the control panel 8, and the communication
unit 90.
The auxiliary storage device 93 may include a storage device such
as a magnetic hard disk device or a semiconductor storage device.
The auxiliary storage device 93 stores information, such as
programs.
The communication unit 90 includes a communication interface for
connecting the image forming apparatus 1 to an external device. The
communication unit 90 communicates with an external device via the
communication interface.
The fixing device 30 will be described in detail.
FIG. 3 is a front cross-sectional view of a heating device
according to the embodiment. The heating device according to the
embodiment is the fixing device 30. The fixing device 30 includes a
pressure roller 30p and a film unit 30h.
The pressure roller 30p forms the nip N with the film unit 30h.
The pressure roller 30p pressurizes the toner image of the sheet S
that entered the nip N. The pressure roller 30p rotates and conveys
the sheet S. The pressure roller 30p includes a cored bar 32, an
elastic layer 33, and a release layer 34.
The cored bar 32 is formed of a metal material such as stainless
steel in a cylindrical shape. Both end portions in the axial
direction of the cored bar 32 are rotatably supported. The cored
bar 32 is rotationally driven by a motor (not shown). The cored bar
32 abuts on a cam member (not shown). The cam member rotates and
moves the cored bar 32 toward and away from the film unit 30h.
The elastic layer 33 is formed of an elastic material such as
silicone rubber. The elastic layer 33 is formed on the outer
peripheral surface of the cored bar 32 with a constant
thickness.
The release layer 34 is formed of a resin material such as
perfluoroalkoxy (PFA) (such as tetrafluoroethylene/perfluoroalkyl
vinyl ether copolymer). The release layer 34 is formed on the outer
peripheral surface of the elastic layer 33.
For example, when the outer diameter of the pressure roller 30p is
20 millimeters (mm) to 40 mm, it is preferable that the outer
diameter of the cored bar 32 is set to 10 mm to 20 mm, the
thickness of the elastic layer 33 is set to 5 mm to 20 mm, and the
thickness of the release layer 34 is set to 20 micrometers (.mu.m)
to 40 .mu.m. The hardness of the outer peripheral surface of the
pressure roller 30p is desirably 40.degree. to 70.degree. at a load
of 9.8 N, as measured with an ASKER-C hardness meter. Thereby, the
area of the nip N and the durability of the pressure roller 30p are
ensured. The pressure roller 30p can be brought into contact with
and separated from the film unit 30h by a link mechanism using a
cam, for example. When the pressure roller 30p is brought into
contact with the film unit 30h and pressed by a pressure spring,
the nip N is formed. On the other hand, when the sheet S is jammed
in the fixing device 30, the sheet S can be removed by separating
the pressure roller 30p from the film unit 30h. In addition, in a
state where a cylindrical film 35 is stopped from rotating, such as
during sleep, the cylindrical film 35 is prevented from being
plastically deformed by separating the pressure roller 30p from the
film unit 30h.
The pressure roller 30p is rotationally driven by a motor and
rotates. When the pressure roller 30p rotates in a state where the
nip N is formed, the cylindrical film 35 of the film unit 30h is
driven to rotate. The pressure roller 30p conveys the sheet S in a
conveyance direction W by rotating in a state where the sheet S is
disposed at the nip N.
The film unit 30h heats the toner image of the sheet S that entered
the nip N. The film unit 30h includes the cylindrical film 35
(cylindrical body), a heater unit 40, a first heat absorbing (e.g.,
soaking, etc.) member 49 (first heat transfer unit), a second heat
absorbing member 50 (second heat transfer unit), a lubricating
layer 51, a support member 36, a stay 38, a heater thermometer 62,
a thermostat 68, and a film thermometer 64. The cylindrical film 35
is formed in (rolled into) a cylindrical shape. The cylindrical
film 35 includes abase layer, an elastic layer, and a release layer
in order from the inner peripheral side. The base layer is formed
of a material such as nickel (Ni) in a cylindrical shape. The
elastic layer is laminated on the outer peripheral surface of the
base layer. The elastic layer is formed of an elastic material such
as silicone rubber. The release layer is laminated on the outer
peripheral surface of the elastic layer. The release layer is
formed of a material such as PFA resin.
In order to shorten a warm-up time, it is preferable to set the
thicknesses of the elastic layer and the release layer so that the
respective heat capacities are not too large. For example, when the
inner diameter of the cylindrical film 35 is 20 mm to 40 mm, the
thickness of the base layer may be set to 30 .mu.m to 50 .mu.m, the
thickness of the elastic layer may be set to 100 .mu.m to 300
.mu.m, and the thickness of the release layer may be set to 20
.mu.m to 40 .mu.m. A coat (for example, a fluorine coat) may be
applied to the inner side of the base layer in order to improve the
frictional slidability with the first heat absorbing member 49.
FIG. 4 is a front cross-sectional view of the heater unit taken
along line IV-IV in FIG. 5. FIG. 5 is a bottom view of the heater
unit (viewed from the +z-direction). The heater unit 40 includes a
substrate 41 (heating element substrate), a heating element set 45,
and a wiring set 55.
The substrate 41 is formed of a metal material such as stainless
steel or a ceramic material such as aluminum nitride. The substrate
41 is formed in along and thin rectangular plate shape. The
substrate 41 is disposed inside the cylindrical film 35 in the
radial direction. In the substrate 41, the axial direction of the
cylindrical film 35 is taken as a longitudinal direction. In other
words, a central axis of the cylindrical film 35 (around which the
cylindrical film 35 extends) is orthogonal to a central axis of the
substrate 41.
In the present application, the x-direction, the y-direction, and
the z-direction are defined as follows.
The y-direction is the longitudinal direction of the substrate 41
(heater unit 40). As will be described later, the +y-direction is a
direction from a central heating element 45a toward a first end
heating element 45b1.
The x-direction is the short direction of the substrate 41. The
+x-direction is the conveyance direction (downstream direction) of
the sheet S.
The z-direction is the normal direction of the substrate 41. The
+z-direction is a direction in which the heating element set 45 is
disposed with respect to the substrate 41. An insulating layer 43
is formed of a glass material or the like on the surface of the
substrate 41 in the +z-direction. The surface of the heater unit 40
in the +z-direction (first surface 40a) faces the inner peripheral
surface of the cylindrical film (see FIG. 3) across the first heat
absorbing member 49. The heating element set 45 is disposed on the
substrate 41. The heating element set 45 is formed on the surface
of the insulating layer 43 in the +z-direction as shown in FIG. 4.
The heating element set 45 is formed of silver/palladium alloy or
the like. The outer shape of the heating element set 45 is formed
in a rectangular shape in which the y-direction is the longitudinal
direction and the x-direction is the short direction.
As shown in FIG. 5, the heating element set 45 includes a plurality
of heating elements 45b1, 45a, and 45b2 provided along the
y-direction. The heating element set 45 includes the first end
heating element 45b1, the central heating element 45a, and the
second end heating element 45b2, which are disposed side by side in
the y-direction.
The central heating element 45a is disposed at the center portion
in the y-direction of the heating element set 45. The central
heating element 45a may be configured by combining a plurality of
small heating elements disposed side by side in the
y-direction.
The first end heating element 45b1 is disposed in the +y-direction
of the central heating element 45a and at the end portion in the
+y-direction of the heating element set 45.
The second end heating element 45b2 is disposed in the -y-direction
of the central heating element 45a and at the end portion in the
-y-direction of the heating element set 45.
A boundary line between the central heating element 45a and the
first end heating element 45b1 is disposed in parallel with the
x-direction. The boundary line between the central heating element
45a and the first end heating element 45b1 may be disposed to
intersect the x-direction. The same applies to the boundary line
between the central heating element 45a and the second end heating
element 45b2.
The heating element set 45 generates heat by electric conduction.
The electric resistance value of the central heating element 45a is
smaller than the electric resistance values of the first end
heating element 45b1 and the second end heating element 45b2. The
electrical resistance values of the first end heating element 45b1
and the second end heating element 45b2 are substantially the same.
Here, the electrical resistance value of the central heating
element 45a is a "central resistance value A", and the electrical
resistance value of the first end heating element 45b1 (second end
heating element 45b2) is an "end resistance value B". For example,
the ratio (A:B) between the central resistance value A and the end
resistance value B is preferably in the range of 3:1 to 7:1, and
more preferably in the range of 4:1 to 6:1.
The sheet S having a small width in the y-direction passes through
the center portion in the y-direction of the fixing device 30. In
this case, the control unit 6 causes only the central heating
element 45a to generate heat. On the other hand, the control unit 6
causes the entire heating element set 45 to generate heat when the
sheet S has a large width in the y-direction. Therefore, the
central heating element 45a, the first end heating element 45b1,
and the second end heating element 45b2 are controlled to generate
heat independently of each other. Further, the first end heating
element 45b1 and the second end heating element 45b2 are similarly
controlled in heat generation.
The wiring set 55 is formed of a metal material such as silver. The
wiring set 55 includes a central contact 52a, a central wiring 53a,
an end contact 52b, a first end wiring 53b1, a second end wiring
53b2, a common contact 58, and a common wiring 57. The central
contact 52a is disposed in the -y-direction of the heating element
set 45.
The central wiring 53a is disposed in the +x-direction of the
heating element set 45. The central wiring 53a connects the
+x-direction end of the central heating element 45a and the central
contact 52a to each other.
The end contact 52b is disposed in the -y-direction of the central
contact 52a.
The first end wiring 53b1 is disposed in the +x-direction of the
heating element set 45 and in the +x-direction of the central
wiring 53a. The first end wiring 53b1 connects the end in
+x-direction of the first end heating element 45b1 and the end
portion in +x-direction of the end contact 52b to each other.
The second end wiring 53b2 is disposed in the +x-direction of the
heating element set 45 and in the -x-direction of the central
wiring 53a. The second end wiring 53b2 connects the end in
+x-direction of the second end heating element 45b2 and the end
portion in -x-direction of the end contact 52b to each other.
The common contact 58 is disposed in the +y-direction of the
heating element set 45.
The common wiring 57 is disposed in the -x-direction of the heating
element set 45. The common wiring 57 connects the common contact
point 58 to the -x-direction ends of the central heating element
45a, the first end heating element 45b1, and the second end heating
element 45b2.
Thus, in the +x-direction of the heating element set 45, the second
end wiring 53b2, the central wiring 53a, and the first end wiring
53b1 are disposed. On the other hand, only the common wiring 57 is
disposed in the -x-direction of the heating element set 45.
Therefore, a center 45c in the x-direction of the heating element
set 45 is disposed in the -x-direction from a center 41c in the
x-direction of the substrate 41.
As shown in FIG. 3, a straight line CL connecting a center pc of
the pressure roller 30p and a center hc of the film unit 30h is
defined. The center 41c in the x-direction of the substrate 41 is
disposed in the +x-direction from the straight line CL. A center
49c in the x-direction of the first heat absorbing member 49
coincides with the center 41c in the x-direction of the substrate
41. The +x-direction end (the downstream end in the conveyance
direction of the sheet S) of the first heat absorbing member 49
coincides with the +x-direction end of the substrate 41. As a
result, since the first heat absorbing member 49 extends in the
+x-direction of the nip N, the sheet S that passed through the nip
N is easily released from the film unit 30h.
The center 45c in the x-direction of the heating element set 45 is
disposed on the straight line CL. The heating element set 45 is
entirely included in the region of the nip N and is disposed at the
center of the nip N. Thereby, the heat distribution in the nip N
becomes uniform, and the sheet S passing through the nip N is
heated uniformly.
As shown in FIG. 4, the heating element set 45 and the wiring set
55 are formed on the surface of the insulating layer 43 in the
+z-direction. A protective layer 46 is formed of a glass material
or the like so as to cover the heating element set 45 and the
wiring set 55. The protective layer 46 protects the heating element
set 45 and the wiring set 55.
As shown in FIG. 3, the heater unit 40 is disposed inside the
cylindrical film 35. The surface of the heater unit 40 in the
+z-direction (see the first surface 40a in FIG. 4) faces the nip N
across the first heat absorbing member 49.
In the first heat absorbing member 49, the axial direction of the
cylindrical film 35 is taken as a longitudinal direction. In other
words, a central axis of the cylindrical film 35 (around which the
cylindrical film 35 extends) is orthogonal to a central axis of the
heat absorbing member 49.
The first heat absorbing member 49 is formed in a rectangular plate
shape. The outer shape of the first heat absorbing member 49 is
equal to the outer shape of the substrate 41 of the heater unit 40.
The first heat absorbing member 49 preferably has the same length
as the substrate 41 of the heater unit 40 in the x-direction and
the y-direction.
The first heat absorbing member 49 is disposed between the inner
surface of the cylindrical film 35 and the heater unit 40. The
first heat absorbing member 49 is disposed on the heating element
set 45 side of the substrate 41 of the heater unit 40. The first
heat absorbing member 49 is disposed in contact with the surface of
the heater unit 40 in the +z-direction (see the first surface 40a
in FIG. 4).
The first heat absorbing member 49 has a higher thermal
conductivity than the substrate 41 of the heater unit 40.
Additionally, the first heat absorbing member 49 has a higher
thermal conductivity than the second heat absorbing member 50. For
example, when the substrate 41 and the second heat absorbing member
50 are made of stainless steel, the first heat absorbing member 49
may be formed of a metal material such as copper or aluminum, or
carbon. The thickness of the first heat absorbing member 49 is
preferably equal to or less than the thickness of the second heat
absorbing member 50.
In the second heat absorbing member 50, the axial direction of the
cylindrical film 35 is taken as a longitudinal direction. In other
words, a central axis of the cylindrical film 35 (around which the
cylindrical film 35 extends) is orthogonal to a central axis of the
second heat absorbing member 50.
The second heat absorbing member 50 is formed in a rectangular
plate shape like the first heat absorbing member 49. The second
heat absorbing member 50 is formed of a member different from the
first heat absorbing member 49. For example, the first heat
absorbing member 49 may be structurally separate from the second
heat absorbing member 50 such that the first heat absorbing member
49 is separable from the second heat absorbing member 50. The outer
shape of the second heat absorbing member 50 is equal to the outer
shape of the substrate 41 of the heater unit 40. The second heat
absorbing member 50 preferably has the same length as the substrate
41 of the heater unit 40 in the x-direction and the
y-direction.
The second heat absorbing member 50 is disposed between the heater
unit 40 and the support member 36. The second heat absorbing member
50 is disposed on the opposite side to the heating element set 45
side of the substrate 41 of the heater unit 40. The second heat
absorbing member 50 is disposed in contact with the surface of the
heater unit 40 in the -z-direction (see the second surface 40b in
FIG. 4).
The second heat absorbing member 50 has a higher thermal
conductivity than the substrate 41 of the heater unit 40. The
second heat absorbing member 50 has a lower thermal conductivity
than the first heat absorbing member 49. For example, when the
substrate 41 is made of stainless steel and the first heat
absorbing member 49 is made of copper, the second heat absorbing
member 50 may be formed of a metal material such as aluminum. A
contact area A2 between the second heat absorbing member 50 and the
support member 36 is smaller than a contact area A1 between the
first heat absorbing member 49 and the heater unit (A2<A1). The
contact surface (the surface in the -z-direction) with the heater
unit 40 in the first heat absorbing member 49 is a flat surface.
The contact surface (the surface in the -z-direction) with the
support member 36 in the second heat absorbing member 50 is a flat
surface.
The lubricating layer 51 is disposed between the inner surface of
the cylindrical film 35 and the first heat absorbing member 49. For
example, the lubricating layer 51 may be a fluorine coat formed on
the surface of the first heat absorbing member 49 in the
+z-direction (first surface 49a). The lubricating layer 51 is
formed over the entire first surface 49a of the first heat
absorbing member 49. As a result, relatively movement between the
first heat absorbing member 49 and the cylindrical film 35 is
facilitated.
The thickness of the lubricating layer 51 is preferably set so as
not to hinder the transfer of heat from the heater unit 40 to the
cylindrical film 35 as much as possible. For example, the thickness
of the lubricating layer 51 is preferably set to 1 .mu.m or more
and 100 .mu.m or less.
Grease (not shown) may be applied to the inner peripheral surface
of the cylindrical film 35. In this case, the grease is disposed
between the lubricating layer 51 (see FIG. 3) and the inner
peripheral surface of the cylindrical film 35. The first heat
absorbing member 49 is in contact with the inner peripheral surface
of the cylindrical film 35 through the lubricating layer 51 and the
grease. When the heater unit 40 generates heat, the viscosity of
the grease decreases. Thus, the slidability between the first heat
absorbing member 49 and the cylindrical film 35 is ensured.
The support member 36 is formed of an elastic material such as
silicone rubber or fluorine rubber, or a resin material such as a
polyimide resin, polyphenylene sulfide (PPS), polyethersulfone
(PES), or a liquid crystal polymer. The support member 36 is
disposed so as to cover the heater unit 40 in the -z-direction and
both sides in the x-direction. The support member 36 supports the
heater unit 40 via the second heat absorbing member 50. Round
chamfers are formed at both end portions in the x-direction of the
support member 36. The support member 36 supports the inner
peripheral surface of the cylindrical film 35 at both end portions
in the x-direction of the heater unit 40.
When the sheet S passing through the fixing device 30 is heated, a
temperature distribution is generated in the heater unit 40
according to the size of the sheet S. When the heater unit 40
becomes locally high in temperature, there is a possibility that
the temperature exceeds the heat resistance temperature of the
support member 36 formed of a resin material. The second heat
absorbing member 50 distributes the temperature produced by the
heater unit 40. Thus, the support member 36 is protected from
relatively high temperatures.
The stay 38 is formed of a steel plate material or the like. A
cross section perpendicular to the y-direction of the stay 38 is
formed in a U-shape. For example, the stay 38 may be formed by
bending a steel material having a plate thickness of 1 mm to 3 mm.
The stay 38 is mounted in the -z-direction of the support member 36
so as to close the U-shaped opening with the support member 36. The
stay 38 extends in the y-direction. Both end portions in the
y-direction of the stay 38 are fixed to the housing of the image
forming apparatus 1. Thus, the film unit 30h is supported by the
image forming apparatus 1. The stay 38 improves the bending
rigidity of the film unit 30h. Near both end portions in the
y-direction of the stay 38, flanges (not shown) that restrict the
movement of the cylindrical film 35 in the y-direction are
mounted.
The heater thermometer 62 is disposed in the -z-direction of the
heater unit 40 with the second heat absorbing member 50 sandwiched
therebetween. For example, the heater thermometer 62 may be a
thermistor. The heater thermometer 62 is mounted and supported on
the surface of the support member 36 in the -z-direction. The
temperature sensing element of the heater thermometer 62 contacts
the second heat absorbing member 50 through a hole penetrating the
support member 36 in the z-direction. The heater thermometer 62
measures the temperature of the heater unit 40 via the second heat
absorbing member 50.
The thermostat 68 is disposed in the same manner as the heater
thermometer 62. The thermostat 68 is incorporated in an electric
circuit described later. The thermostat 68 cuts off the electric
conduction to the heating element set 45 when the temperature of
the heater unit 40 detected via the second heat absorbing member 50
exceeds a predetermined temperature (target temperature).
FIG. 6 is a plan view of the heater thermometer and the thermostat
(viewed from the -z-direction). In FIG. 6, the illustration of the
support member 36 is omitted. In addition, the following
description regarding the arrangement of the heater thermometer,
the thermostat, and the film thermometer demonstrates the
arrangement of each temperature sensing element.
A plurality of heater thermometers 62 (62a and 62b) are disposed
side by side in the y-direction. The plurality of heater
thermometers 62 are disposed on the heating element set 45. The
plurality of heater thermometers 62 are disposed within a range in
the y-direction of the heating element set 45. The plurality of
heater thermometers 62 are disposed at the center in the
x-direction of the heating element set 45. That is, when viewed
from the z-direction, the plurality of heater thermometers 62 and
the heating element set 45 overlap at least partially.
The plurality of thermostats 68 (68a and 68b) are also disposed in
the same manner as the plurality of heater thermometers 62
described above.
The plurality of heater thermometers 62 include a central heater
thermometer 62a and an end heater thermometer 62b (a thermometer
disposed on one side in the longitudinal direction).
The central heater thermometer 62a measures the temperature of the
central heating element 45a. The central heater thermometer 62a is
disposed within the range of the central heating element 45a. That
is, when viewed from the z-direction, the central heater
thermometer 62a and the central heating element 45a overlap.
The end heater thermometer 62b measures the temperature of the
second end heating element 45b2. As described above, the first end
heating element 45b1 and the second end heating element 45b2 are
similarly controlled in heat generation. Therefore, the temperature
of the first end heating element 45b1 is equal to the temperature
of the second end heating element 45b2. The end heater thermometer
62b is disposed within the range of the second end heating element
45b2. That is, when viewed from the z-direction, the end heater
thermometer 62b and the second end heating element 45b2 overlap
each other.
The plurality of thermostats 68 include a central thermostat 68a
and an end thermostat 68b.
The central thermostat 68a cuts off the electric conduction to the
heating element set 45 when the temperature of the central heating
element 45a exceeds a predetermined temperature (target
temperature). The central thermostat 68a is disposed within the
range of the central heating element 45a. That is, when viewed from
the z-direction, the central thermostat 68a and the central heating
element 45a overlap each other.
The end thermostat 68b cuts off the electric conduction to the
heating element set 45 when the temperature of the first end
heating element 45b1 exceeds a predetermined temperature (target
temperature). As described above, the first end heating element
45b1 and the second end heating element 45b2 are similarly
controlled in heat generation. Therefore, the temperature of the
first end heating element 45b1 is equal to the temperature of the
second end heating element 45b2. The end thermostat 68b is disposed
within the range of the first end heating element 45b1. That is,
when viewed from the z-direction, the end thermostat 68b and the
first end heating element 45b1 overlap each other.
As described above, the central heater thermometer 62a and the
central thermostat 68a are disposed on the central heating element
45a. Thus, the temperature of the central heating element 45a is
measured. Further, when the temperature of the central heating
element 45a exceeds a predetermined temperature (target
temperature), the electric conduction to the heating element set 45
is cut off.
The end heater thermometer 62b is disposed on the second end
heating element 45b2 (end heating element). Thus, the temperature
of the second end heating element 45b2 is measured. Since the
temperature of the first end heating element 45b1 is equal to the
temperature of the second end heating element 45b2, the
temperatures of the first end heating element 45b1 and the second
end heating element 45b2 are measured.
The end thermostat 68b is disposed on the first end heating element
45b1. When the temperatures of the first end heating element 45b1
and the second end heating element 45b2 exceed a predetermined
temperature (target temperature), the electric conduction to the
heating element set 45 is cut off.
The plurality of heater thermometers 62 and the plurality of
thermostats 68 are alternately disposed in parallel along the
y-direction. As described above, the first end heating element 45b1
is disposed in the +y-direction of the central heating element 45a.
The end thermostat 68b is disposed within the range of the first
end heating element 45b1. The central heater thermometer 62a is
disposed in the +y-direction from the center in the y-direction of
the central heating element 45a. The central thermostat 68a is
disposed in the -y-direction from the center in the y-direction of
the central heating element 45a. As described above, the second end
heating element 45b2 is disposed in the -y-direction of the central
heating element 45a. The end heater thermometer 62b is disposed
within the range of the second end heating element 45b2. Thus, the
end thermostat 68b, the central heater thermometer 62a, the central
thermostat 68a, and the end heater thermometer 62b are disposed
side by side in this order from the +y-direction to the
-y-direction. In general, the thermostat 68 connects (completes)
and disconnects (interrupts) an electric circuit by using a
deformation of a curved bimetal element which is caused by a
temperature change of the bimetal element. The thermostat is formed
long and thin in accordance with the shape of the bimetal. Further,
the terminals extend outward from both end portions in the
longitudinal direction of the thermostat 68. An external wiring
connector is connected to this terminal by caulking. Therefore, it
is necessary to secure a space outside the thermostat 68 in the
longitudinal direction. Since the fixing device 30 has no space in
the x-direction, the longitudinal direction of the thermostat 68 is
disposed along the y-direction. At this time, if the plurality of
thermostats 68 are disposed adjacent to each other in the
y-direction, it is difficult to secure a connection space for
external wiring.
As described above, the plurality of heater thermometers 62 and the
plurality of thermostats 68 are alternately disposed in parallel
along the y-direction. Accordingly, the heater thermometer 62 is
disposed adjacent to the thermostat 68 in the y-direction.
Therefore, a connection space for external wiring to the thermostat
68 can be secured. Moreover, the degree of freedom of the layout in
the y-direction of the thermostat 68 and the heater thermometer 62
increases. As a result, the thermostat 68 and the heater
thermometer 62 can be disposed at optimal positions, and the
temperature of the fixing device 30 can be controlled. Further, it
is easy to separate the alternating current wiring connected to the
plurality of thermostats 68 and the direct current wiring connected
to the plurality of heater thermometers 62 from each other. Thus,
the generation of noise in an electric circuit is suppressed. The
film thermometer 64 is disposed inside the cylindrical film 35 and
in the +x-direction of the heater unit 40, as shown in FIG. 3. The
film thermometer 64 contacts the inner peripheral surface of the
cylindrical film 35 and measures the temperature of the cylindrical
film 35.
FIG. 7 is an electric circuit diagram of the heating device
according to the embodiment. In FIG. 7, the bottom view of FIG. 5
is disposed on the upper side of the page and the plan view of FIG.
6 is disposed on the lower side of the page. In FIG. 7, a plurality
of film thermometers 64 along with the cross section of the
cylindrical film 35 are illustrated above the plan view on the
lower side. The plurality of film thermometers include a central
film thermometer 64a and an end film thermometer 64b (a thermometer
disposed on one side in the longitudinal direction).
The central film thermometer 64a contacts the center portion in the
y-direction of the cylindrical film 35. The central film
thermometer 64a contacts the cylindrical film 35 within the range
in the y-direction of the central heating element 45a. The central
film thermometer 64a measures the temperature of the center portion
in the y-direction of the cylindrical film 35.
The end film thermometer 64b contacts the end portion in the
-y-direction of the cylindrical film 35. The end film thermometer
64b contacts the cylindrical film 35 within the range in the
y-direction of the second end heating element 45b2. The end film
thermometer 64b measures the temperature of the end portion in the
-y-direction of the cylindrical film 35. As described above, the
first end heating element 45b1 and the second end heating element
45b2 are similarly controlled in heat generation. Therefore, the
temperature of the end portion in the -y-direction of the
cylindrical film 35 is equal to the temperature of the end portion
in the +y-direction.
A power supply 95 is connected to the central contact 52a via a
central triac 96a. The power supply 95 is connected to the end
contact 52b via an end triac 96b. The CPU 91 controls ON and OFF of
the central triac 96a and the end triac 96b independently of each
other. When the CPU 91 turns on the central triac 96a, power is
supplied from the power supply 95 to the central heating element
45a. As a result, the central heating element 45a generates heat.
When the CPU 91 turns on the end triac 96b, power is supplied from
the power supply 95 to the first end heating element 45b1 and the
second end heating element 45b2. As a result, the first end heating
element 45b1 and the second end heating element 45b2 generate heat.
As described above, the central heating element 45a, the first end
heating element 45b1, and the second end heating element 45b2 are
controlled to generate heat independently of each other. The
central heating element 45a, the first end heating element 45b1,
and the second end heating element 45b2 are connected in parallel
to the power supply 95.
The power supply 95 is connected to the common contact 58 via the
central thermostat 68a and the end thermostat 68b. The central
thermostat 68a and the end thermostat 68b are connected in
series.
When the temperature of the central heating element 45a rises
abnormally, the detected temperature of the central thermostat 68a
exceeds a predetermined temperature (target temperature). At this
time, the central thermostat 68a cuts off the electric conduction
from the power supply 95 to the entire heating element set 45.
When the temperature of the first end heating element 45b1 rises
abnormally, the detected temperature of the end thermostat 68b
exceeds a predetermined temperature (target temperature). At this
time, the end thermostat 68b cuts off the electric conduction from
the power supply 95 to the entire heating element set 45. As
described above, the first end heating element 45b1 and the second
end heating element 45b2 are similarly controlled in heat
generation. Therefore, when the temperature of the second end
heating element 45b2 rises abnormally, the temperature of the first
end heating element 45b1 rises similarly. Therefore, when the
temperature of the second end heating element 45b2 rises
abnormally, the end thermostat 68b similarly cuts off the electric
conduction from the power supply 95 to the entire heating element
set 45.
The CPU 91 (control unit 6) measures the temperature of the central
heating element 45a with the central heater thermometer 62a. The
CPU 91 measures the temperature of the second end heating element
45b2 with the end heater thermometer 62b. The temperature of the
second end heating element 45b2 is equal to the temperature of the
first end heating element 45b1. The CPU 91 measures the temperature
of the heating element set 45 with the heater thermometer 62 when
the fixing device 30 is started. When the temperature of the
heating element set 45 is lower than a predetermined temperature
(target temperature), the CPU 91 causes the heating element set 45
to generate heat only for a short time. Thereafter, the CPU 91
starts to rotate the pressure roller 30p. Due to the heat generated
by the heating element set 45, the viscosity of the grease applied
to the inner peripheral surface of the cylindrical film 35 is
reduced. Thus, the slidability between the first heat absorbing
member 49 and the cylindrical film 35 at the time of starting the
rotation of the pressure roller 30p is ensured.
The CPU 91 measures the temperature of the center portion in the
y-direction of the cylindrical film 35 with the central film
thermometer 64a. The CPU 91 measures the temperature of the end
portion in the -y-direction of the cylindrical film 35 with the end
film thermometer 64b. The temperature of the end portion in the
-y-direction of the cylindrical film 35 is equal to the temperature
of the end portion in the +y-direction of the cylindrical film 35.
The CPU 91 measures the temperatures at the center portion and the
end portion in the y-direction of the cylindrical film 35 when the
fixing device 30 is in operation. The CPU 91 performs phase control
or wave number control on the power supplied to the heating element
set 45 by the central triac 96a and the end triac 96b. The CPU 91
controls the electric conduction to the central heating element 45a
based on the temperature measurement result of the center portion
in the y-direction of the cylindrical film 35. The CPU 91 controls
the electric conduction to the first end heating element 45b1 and
the second end heating element 45b2 based on the temperature
measurement result of the end portion in the y-direction of the
cylindrical film 35.
As described above, the fixing device 30 according to the
embodiment includes the cylindrical film 35, the heater unit 40,
the support member 36, the first heat absorbing member 49, and the
second heat absorbing member 50. The cylindrical film 35 has a film
shape. The heater unit 40 is disposed inside the cylindrical film
35. In the heater unit 40, the axial direction of the cylindrical
film 35 is taken as the longitudinal direction. In other words, a
central axis of the cylindrical film 35 (around which the
cylindrical film 35 extends) is orthogonal to a central axis of the
heater unit 40. The support member 36 supports the heater unit 40.
The first heat absorbing member 49 is disposed between the inner
surface of the cylindrical film 35 and the heater unit 40. The
first heat absorbing member 49 abuts on the first surface 40a of
the heater unit 40. The second heat absorbing member 50 is disposed
between the heater unit 40 and the support member 36. The second
heat absorbing member 50 abuts on the second surface 40b of the
heater unit 40 opposite to the first surface 40a. With the above
configuration, the following effects can be obtained.
The heater unit 40 is sandwiched between the first heat absorbing
member 49 and the second heat absorbing member 50. Therefore, it is
possible to suppress variation in the temperature distribution of
the front and back surfaces (the first surface 40a and the second
surface 40b) of the heater unit 40 in the longitudinal direction.
Therefore, the heat produced by the heater unit 40 can be
distributed.
As a result, it is possible to suppress damage to the cylindrical
film 35 due to a temperature rise in the non-sheet passing area
(the area where the sheet does not pass) and to suppress damage to
the support member 36.
In addition, the heat produced by the heater unit 40 can be more
effectively distributed as compared with the case where the heat
absorbing member is disposed only on one of the first surface 40a
and the second surface 40b of the heater unit 40. The first heat
absorbing member 49 has a higher thermal conductivity than the
second heat absorbing member 50. With the above configuration, the
following effects can be obtained.
The heat of the heater unit 40 is easily transferred to the
cylindrical film 35 and the heat of the heater unit 40 is not
easily transferred to the support member 36. That is, the heat of
the heater unit 40 is less likely to escape (dissipate) to the
support member 36 side. Therefore, the heat produced by the heater
unit 40 can be distributed without greatly deteriorating the
temperature raising performance of the cylindrical film 35.
The first heat absorbing member 49 and the second heat absorbing
member 50 have a higher thermal conductivity than the substrate 41
of the heater unit 40. With the above configuration, the following
effects can be obtained.
Compared with the case where at least one of the first heat
absorbing member 49 and the second heat absorbing member 50 has a
thermal conductivity equal to or lower than the substrate 41 of the
heater unit 40, the heat produced by the heater unit 40 can be more
effectively distributed.
The heater unit 40 includes the substrate 41 and the heating
elements 45b1, 45a, and 45b2 disposed on the surface of the
substrate 41 facing the first heat absorbing member 49. With the
above configuration, the following effects can be obtained.
Compared with the case where the first heat absorbing member 49 is
disposed on the opposite side to the heating elements 45b1, 45a,
and 45b2 of the substrate 41, the heat of the heating elements
45b1, 45a, and 45b2 is easily transferred to the cylindrical film
35. Therefore, the heat produced by the heater unit 40 can be
distributed without greatly deteriorating the temperature raising
performance of the cylindrical film 35.
The cylindrical film 35 forms the nip N with the pressure roller
30p. The heater unit 40 faces the nip N. With the above
configuration, the following effects can be obtained.
Compared to the case where the heater unit 40 is disposed offset
from the nip N, the heat distribution in the nip N tends to be
uniform. Therefore, the sheet S passing through the nip N can be
heated uniformly.
The fixing device 30 includes the lubricating layer 51 disposed
between the inner surface of the cylindrical film 35 and the first
heat absorbing member 49. With the above configuration, the
following effects can be obtained.
The slidability between the first heat absorbing member 49 and the
cylindrical film 35 can be ensured.
The thickness of the lubricating layer 51 is 1 .mu.m or more and
100 .mu.m or less. With the above configuration, the following
effects can be obtained.
While ensuring the slidability between the first heat absorbing
member 49 and the cylindrical film 35, it is possible to prevent
the heat transfer from the heater unit 40 to the cylindrical film
35 from being hindered.
The contact area A2 between the second heat absorbing member 50 and
the support member 36 is smaller than the contact area A1 between
the first heat absorbing member 49 and the heater unit 40. With the
above configuration, the following effects can be obtained.
Compared with the case of A2.gtoreq.A1, the heat of the heater unit
40 is less likely to escape to the support member 36 side.
Therefore, the heat produced by the heater unit 40 can be
distributed without greatly deteriorating the temperature raising
performance of the cylindrical film 35.
The first heat transfer unit is the plate-shaped first heat
absorbing member 49 taking the axial direction of the cylindrical
film 35 as a longitudinal direction. The second heat transfer unit
is the plate-like second heat absorbing member 50 formed of a
member different from the first heat absorbing member 49. With the
above configuration, there is an effect that the thermal
conductivity of the first heat transfer unit and the second heat
transfer unit is easily set with a simple configuration.
The image forming apparatus 1 according to the embodiment includes
the fixing device 30 described above.
The fixing device 30 can distribute the heat produced by the heater
unit 40. Therefore, the image forming apparatus 1 can improve the
image quality.
Next, a modification example of the embodiment will be
described.
The first heat absorbing member 49 according to the embodiment has
a higher thermal conductivity than the second heat absorbing member
50. On the other hand, the first heat absorbing member 49 may have
a thermal conductivity equal to or lower than the second heat
absorbing member 50.
The first heat absorbing member 49 according to the embodiment is
disposed on the side of the heating elements 45b1, 45a, and 45b2 of
the substrate 41. On the other hand, the first heat absorbing
member 49 may be disposed on the opposite side to the side of the
heating elements 45b1, 45a, and 45b2 of the substrate 41. In this
case, the heating elements 45b1, 45a, and 45b2 are disposed in the
-z-direction with respect to the substrate 41. The heater unit 40
according to the embodiment faces the nip N. On the other hand, the
heater unit 40 may be disposed offset from the nip N. For example,
the fixing device may include a nip forming unit (for example, a
pad for forming the nip N) and a heating unit (for example, a
heater unit disposed at a position different from the pad).
The fixing device 30 according to the embodiment includes the
lubricating layer 51 disposed between the inner surface of the
cylindrical film 35 and the first heat absorbing member 49. On the
other hand, the fixing device 30 may not have the lubricating layer
51.
The thickness of the lubricating layer 51 according to the
embodiment is 1 .mu.m or more and 100 .mu.m or less. On the other
hand, the thickness of the lubricating layer 51 may be less than 1
.mu.m or more than 100 .mu.m. For example, the thickness of the
lubricating layer 51 can be changed according to the required
specifications.
The contact area A2 between the second heat absorbing member 50 and
the support member 36 according to the embodiment is smaller than
the contact area A1 between the first heat absorbing member 49 and
the heater unit 40. On the other hand, the contact area A2 between
the second heat absorbing member 50 and the support member 36 may
be equal to or greater than the contact area A1 between the first
heat absorbing member 49 and the heater unit 40.
In the second heat absorbing member 50 according to the embodiment,
the contact surface (the surface in the -z-direction) with the
support member 36 is a flat surface. On the other hand, the contact
surface with the support member 36 in a second heat absorbing
member 150 may be a surface which has an unevenness 150a (see FIG.
8). For example, the unevenness 150a may be formed over the entire
surface of the second heat absorbing member 150 in the
-z-direction. For example, the second heat absorbing member 150 may
abut on the support member 36 by point contact or line contact.
The first heat transfer unit according to the embodiment is the
plate-like first heat absorbing member 49 taking the axial
direction of the cylindrical film 35 as a longitudinal direction.
The second heat transfer unit is the plate-like second heat
absorbing member 50 formed of a member different from the first
heat absorbing member 49. On the other hand, the first heat
transfer unit and the second heat transfer unit may be configured
with a heat absorbing member 249 formed integrally with the same
member (see FIG. 9). For example, the heat absorbing member 249 may
have a U-shape that sandwiches the heater unit 40 when viewed from
the axial direction of the cylindrical film 35. For example, the
heat absorbing member 249 may be biased in a direction in which the
heater unit 40 is sandwiched. According to this configuration, the
heater unit 40 can be supported with a simple configuration.
The image processing apparatus according to the embodiment is the
image forming apparatus 1, and the heating device is the fixing
device 30. On the other hand, the image processing apparatus may be
a decoloring apparatus, and the heating device may be a decoloring
(erasing) unit. The decoloring apparatus performs a process of
decoloring (erasing) an image formed on the sheet with the
decoloring toner. The decoloring unit heats and decolors the
decoloring toner image formed on the sheet passing through the
nip.
According to at least one embodiment described above, the fixing
device 30 includes the cylindrical film 35, the heater unit 40, the
support member 36, the first heat absorbing member 49, and the
second heat absorbing member 50. The cylindrical film 35 has a film
shape. The heater unit 40 is disposed inside the cylindrical film
35. In the heater unit 40, the axial direction of the cylindrical
film 35 is taken as the longitudinal direction. The support member
36 supports the heater unit 40. The first heat absorbing member 49
is disposed between the inner surface of the cylindrical film 35
and the heater unit 40. The first heat absorbing member 49 abuts on
the first surface 40a of the heater unit 40. The second heat
absorbing member 50 is disposed between the heater unit 40 and the
support member 36. The second heat absorbing member 50 abuts on the
second surface 40b of the heater unit 40 opposite to the first
surface 40a. With the above configuration, the following effects
can be obtained.
The heater unit 40 is sandwiched between the first heat absorbing
member 49 and the second heat absorbing member 50. Therefore, it is
possible to suppress variation in the temperature distribution of
the front and back surfaces (the first surface 40a and the second
surface 40b) of the heater unit 40 in the longitudinal direction.
Therefore, the heat produced by the heater unit 40 can be
distributed.
While certain embodiments have been described, these embodiments
have been presented byway of example only, and are not intended to
limit the scope of the present disclosure. Indeed, the embodiments
described herein may be embodied in a variety of other forms;
furthermore, various omissions, substitutions and changes in the
form of the embodiments described herein may be made without
departing from the spirit of the present disclosure. The
accompanying claims and their equivalents are intended to cover
such forms or modifications as would fall within the scope and
spirit of the present disclosure.
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